FR2966114A1 - VEHICLE BRAKE SYSTEM AND METHOD FOR MANAGING SUCH A BRAKE SYSTEM - Google Patents

Abstract

Brake system comprising an actuating element (10), an input piston (16) displaced by the control of the element (10) with a minimum actuating stroke, an output piston (12) receiving the brake force (Fb) exerted by the driver on the element (10) by the displacement of the inlet piston (16), moves and increases the pressure in the piston-cylinder unit. Upon actuation of the element (10) following the stroke (x) less than the minimum stroke a spring installation (20), deforms to prohibit the transmission of force (Fb) on the piston (12); for controlling the element (10) of a stroke (x) smaller than the minimum stroke, the piston (12) is displaced by the amplifier (22) and increases the pressure in the piston-cylinder unit. The invention also relates to a method of managing such a brake system.

Description

FIELD OF THE INVENTION The invention relates to a vehicle braking system comprising: - a brake actuating element, - an input piston which, when controlling the brake actuating element is displaced at least a predetermined minimum actuating stroke from its output position; - an output piston to which the brake force exerted by the driver on the brake actuating element is transmitted by the moving the inlet piston, so as to place the output piston to increase the pressure in a piston-cylinder unit of the brake system, and - a first brake force amplifier. The invention also relates to a method of managing such a vehicle brake system comprising: - a brake actuating element, an input piston which for an actuation of the brake actuating element , is displaced by at least one predefined minimum actuation stroke from its output position so that a brake force exerted by the driver on the brake actuating member is transmitted to a piston of output by the inlet piston, moved, so as to move the output piston and thereby increase the pressure in the piston-cylinder unit of the brake system, 25 - a spring installation which, upon actuation of the a brake actuating element with an actuating stroke different from zero and smaller than the minimum actuating stroke is deformed to prevent transmission of the brake force exerted by the driver by the actuating element of the actuating element. brake moved from the actuating stroke on the output piston; - a first brake force amplifier; and - at least one electric and / or magnetic brake system. STATE OF THE ART Electric vehicles and hybrid vehicles are equipped with a braking system enabling regenerative braking.

2 (dynamic braking) comprising an electric motor driven as a generator for dynamic braking. The electrical energy recovered by the dynamic braking is used after storage, preferably to accelerate the vehicle. This reduces the power lost as in the case of a conventional vehicle, resulting from frequent braking during travel, to reduce energy consumption and the emission of polluting by the electric vehicle or hybrid. However, the operation of a generator of the electric motor, for example of the electric drive motor, generally assumes a certain limit speed of the vehicle. Thus often, dynamic braking is not able to exert on the wheels of the vehicle, a braking torque in generator mode until the vehicle stops. This is why, in addition to the electric motor operating in dynamic mode, a hybrid vehicle generally comprises in addition, a hydraulic brake system that compensates for at least the disappearance of the dynamic braking efficiency at low speeds. In this case, when the electric energy accumulator is loaded to the maximum, it nevertheless allows to apply all the brake torque by the hydraulic brake system if the regenerative brake can no longer exert brake torque on the wheels. . On the other hand, in some cases it is desirable to exert as little hydraulic brake force as possible on the wheels to have a high degree of recovery. For example, after switching operations, the coupled generator is often activated in recovery mode to ensure reliable charging of the intermediate battery and allow high energy savings. In general, the driver prefers the total brake torque applied to the vehicle and corresponding to his control of the brake actuating element, such as for example the actuation of the brake pedal, independently of the implementation or the neutralization of the dynamic brake. Some electric and hybrid vehicles therefore have an automation that adapts the brake torque supplied by the hydraulic brake system to the current brake torque of the regenerative brake to respect a desired total brake torque.

Thus, the driver will not have to adapt the brake torque himself.

3 of the hydraulic brake system to the actual brake torque provided by the recovery brake by appropriate actuation of the actuating element to resume the braking regulator mission. For example, for such an automation, electric cable braking systems and especially EHB systems are however expensive because of their electronic, mechanical and hydraulic means in cable / wire braking systems. DE 10 2009 026 960 A1 discloses a method of controlling a brake actuation of a hybrid vehicle. The brake system used for this purpose preferably has a vacuum stroke between the brake pedal and the master brake cylinder piston. During this idle stroke, a brake force amplifier exerts a force on the brake pedal which opposes the actuation of the brakes by the driver. This solution is intended to ensure that the decoupling of the brake pedal is not noticeable by the driver during the actuation of the brake and at the same time the generator of the hybrid vehicle is used to charge the vehicle battery. Inasmuch as the brake effect exerted by the generator is not sufficient for a braking efficiency used to actuate the brake pedal by the driver, it is necessary to seek by closing at least one shut-off valve and / or by activating at least one hydraulic pump of the brake system, establish a hydraulic brake pressure in the wheel brake cylinders. DESCRIPTION AND ADVANTAGES OF THE INVENTION The subject of the present invention is a brake system of the type defined above, characterized by: a spring installation by means of which the input piston is mounted on the brake actuating element so that, when the actuating element of the brake is actuated with an actuating stroke different from zero and smaller than a minimum actuating stroke, the spring system is deformed so as to transmission of the brake force exerted by the driver, the brake actuating element displaced from the actuating stroke on the output piston;

4 * when the actuating element of the brake is actuated with an actuating stroke different from zero and smaller than the minimum actuating stroke, the output piston is displaced by the first brake force amplifier to thereby increase the pressure in the piston-cylinder unit. The subject of the invention is also a method of managing a brake system as described, this method being characterized by the following steps: detection of the control of the actuating element of the actuating stroke different from zero and less than the minimum actuating stroke and setting a reference quantity relating to the total brake torque to be exerted on the vehicle, taking into account the control of the brake actuating element, - controlling at least one installation of electric and / or magnetic brakes in a mode in which the brake torque of the electric and / or magnetic brake system is less than or equal to the total brake torque corresponding to the fixed set-point magnitude, exerted on at least one the vehicle wheel, and - controlling the first brake force amplifier taking into account the difference between the total brake torque corresponding to the set reference quantity, and the brake torque of the electric and / or magnetic brake system for moving the output piston by the first brake force amplifier and adjusting the pressure in the piston-cylinder unit again.

The present invention utilizes a cost-effective spring arrangement to create a "vacuum stroke" while allowing the spring installation to be used simultaneously as a force simulator (pedal simulator, pedal-trip simulator, or simulator of the pedal). feel of brake pedal). Thanks to the "idle stroke", the control of the brake actuating element, which is for example the brake pedal, with an actuating stroke less than a minimum actuating stroke, does not produce braking. direct driver on the piston-cylinder unit, to increase the pressure in it. Thus, for such a control of the brake actuation system, the braking of the vehicle will be done by the installation of electric and / or electromagnetic (non-hydraulic) brakes, in particular by a dynamic brake installation (brake installation by energy recovery), such as for example a generator without this being linked to an undesirable exceeding of the brake setpoint by the driver. The use of a generator to recharge the vehicle battery, does not produce too abrupt braking of the vehicle and that is why this intervention is not noticeable by the driver. At the same time, the spring installation generates a reaction, so that the driver perceives a pedal sensation (brake pedal feel) to which he is accustomed. The present invention thus provides an economic possibility of achieving the sensation of brake or brake reaction (brake pedal sensation) perceived by the driver. The dynamic brake installation is however only one possible example of an electrical and / or electromagnetic brake installation applying the invention. The installation of electric and / or electromagnetic brakes may also include a parking brake. Another advantage of the invention is that the idle stroke provided by the spring installation can be short-circuited in a simple manner in that the driver controls the brake actuating element at least in the course of the stroke. minimal actuation. The driver can thus participate directly by applying a brake force on the piston-cylinder unit which is for example the master cylinder.

A significant advantage of the spring installation with respect to a brake force amplifier is that the spring installation does not require energy to operate. It is the same for the congestion of the spring installation which is relatively low.

In addition, according to the invention, the first brake force amplifier is used so that if the transmission of the brake force of the driver is prohibited, the amplifier generates a hydraulic brake torque supplementing or replacing the brake torque of the generator . This results in a relatively low generator brake torque by establishing the hydraulic brake torque of the first

6 brake amplifier that provides compensation; this makes it possible to respect the desired total brake torque in a preferential manner as a function of the control of the brake actuating element by the driver. Similarly, in cases in which it is not advantageous to use the generator, the hydraulic brake torque can be exerted instead of the brake torque of the generator by means of the first brake force amplifier. According to the present invention, this is not necessary in case when to establish the hydraulic brake torque, closing the shut-off valves and / or the hydraulic brake torque pumps to activate them. This is related to the advantages in that setting the hydraulic brake torque is relatively simple and fast. Since the establishment of the hydraulic brake torque does not require any exceptional use of hydraulic brake system components, the braking system provided here can be replaced by a large number of brake circuits or different types of hydraulic components. brake circuits. This facilitates the replacement of the hydraulic components in the brake system described above. Drawings The present invention will be described hereinafter in more detail with the aid of embodiments of a vehicle brake system, shown in the accompanying drawings in which: - Figures 1A-1D are schematic views of a first embodiment of the brake system in different operating modes, - Figures 2A-2D are schematic representations of a second embodiment of the brake system in different operating modes, and - Figure 3 is a flow chart showing an embodiment of the method of managing a vehicle brake system according to the invention. DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIGS. 1A-1D schematically show a first embodiment of the brake system for different modes of operation.

The brake system, which is only partially shown in FIGS. 1A-1D, has a brake actuating element 10 in the form of a brake pedal. The braking system described herein, however, is not limited to a brake actuating member 10 constituted by a brake pedal. Alternatively or in addition to a brake pedal, the brake system may also include a brake actuating element 10 for manual control. To brake a vehicle equipped with such a brake system, the system comprises a hydraulic brake system (not shown) with at least one piston-cylinder unit. The piston-cylinder unit includes an output piston 12 so that the displacement of the output piston 12 in the direction of displacement 14, increases the internal pressure in the piston-cylinder unit. For example, the outlet piston 12 can be moved in the direction of movement 14 at least in part to the piston-cylinder unit. A preferential manner corresponds to a piston-cylinder unit with a master cylinder such as for example a tandem master cylinder. The braking system shown schematically is however not limited to a direct arrangement of the output piston 12 on or at least partly in the piston-cylinder unit. The hydraulic braking system (not sketched) of the brake system has at least one brake circuit with at least one wheel brake cylinder hydraulically connected to the piston-cylinder unit so that the increase of the internal pressure in the piston-cylinder unit exerts a hydraulic brake torque on the wheel of the vehicle equipped with the wheel brake cylinder. The brake cylinder described herein is not limited to a certain embodiment for at least one brake circuit and / or a certain type of wheel brake cylinder used.

In particular, in this embodiment of a brake circuit with a hydraulic component, the possibilities of choice are unlimited. For this reason, the description will not further detail the only brake circuit designed in particular for a distribution between the brake circuits in a parallel distribution or a cross distribution (distribution II or X).

The brake system comprises an inlet piston 16 moved from its rest position by the brake actuating element 10 itself displaced by at least a predefined minimum operating stroke. The output position (rest position) of the inlet piston 16 here means the position occupied by the inlet piston 16 when the brake actuating element 10 is not actuated, that is to say when the force Fb exerted on this element by the driver, is zero. The displacement of the input piston 16 transmits the brake force Fb exerted by the driver on the output piston 12 so that the output piston 12 moves and that the displacement of the output piston 12 increases the pressure in the piston unit -cylinder. The transmission of the brake force Fb exerted by the driver, by the inlet piston 16 on the output piston 12, is carried out for example by the reaction disc 18, interposed. The inlet piston 16 can contact the corresponding face of the reaction disk 18 facing the brake actuating element 10, while the output piston 12 is on the side of the reaction disk 18 opposite the side facing the rotor. However, it should be noted that the reaction disc 18 is only one example of a resilient force transmission element between the output piston 12 and the inlet piston. 16. Similarly, the braking system described here is not limited to such equipment with an elastic force transmission element. The brake system comprises a spring arrangement 20 which connects the input piston 16 to the brake actuating member 10 or is connected to this brake actuating member. The spring assembly 20 is mounted between the brake actuating member 10 and the inlet piston 16 so that when the brake actuating member 10 is controlled, the spring arrangement 20 deforms according to an actuating stroke other than zero and for a minimum actuating stroke, so as to prevent transmission to the output piston 12 of the brake force exerted by the driver according to the actuating stroke moving the actuating element This is achieved for example by the spring arrangement 20 designed to prohibit the transmission of the brake force of the driver of the brake actuating member 10 displaced from the actuating stroke to the brake.

9 output piston 12 because the inlet piston 16 is in its output position. In other words for a displacement of the brake actuating element 10, the spring installation 20 can be retracted and / or compressed by an actuating stroke different from zero, but lower than the stroke of minimum actuation so that the inlet piston 16 remains in its output position and so that the output piston 12 is driven by the input piston 16, moved in the direction of displacement 14. The spring installation 20 thus creates a "vacuum stroke" in which the brake force Fb of the driver can not be transmitted to the output piston 16 and thus can not produce the direct braking action of the driver on the piston-cylinder unit to increase its internal pressure. In other words, the brake actuating element 10 is movable according to the "idle stroke" without the brake force Fb exerted by the driver being transmitted to the output piston 16 and thus producing an increase in pressure in the piston-cylinder unit, the displacement of the brake actuating element 10 of the "vacuum stroke", being hindered or blocked. This "vacuum stroke" can be overcome by the application of a relatively low force by the driver who can participate directly in braking by the piston-cylinder unit by applying a conceivable force. Thus, even in the event of deterioration of the operation of the electrical components of the brake system, for example due to the fact that their power supply is cut off, the driver can nonetheless provide direct braking by acting on the piston-cylinder unit to apply a hydraulic brake torque braking his vehicle. In addition, the deformable spring installation 20 is designed so that its deformation / compression produces a noticeable reaction by the driver in response to his control of the brake actuating member 10. Thus, even for a displacement of the brake actuating element 10 of a stroke different from zero but lower than a minimum stroke, despite the non-driving of the output piston 12 with respect to the piston-cylinder unit, the driver will have a perception or sensation brake actuation / perception

10 (pedal sensation). The reaction of the pedal / restoring force exerted by the spring installation 20 on the actuating element 10 which has been controlled, guarantees a better operating comfort of the brake actuating element 10 for the driver. . In particular, the spring installation 20 may have a spring constant (spring characteristic) force-stroke which corresponds to the feeling of actuation / braking sensation (pedal feel) to which the driver is accustomed. According to an advantageous development, the spring installation 20 has a force-stroke spring constant (characteristic curve) which corresponds to a constant force-stroke of the brake pedal. Advantageously, the spring installation 20 will be detailed more precisely below. The brake system further comprises at least a first brake force amplifier 22 which allows at least upon actuation of the brake actuating element 10 with an actuating stroke different from zero and lower than the stroke. of minimal actuation of the output piston 12, to be moved to increase the internal pressure in the piston-cylinder unit. It is thus possible in the case where the output piston 12 is not displaced by the transmission of the brake force Fb exerted by the driver by the inlet piston 16, to increase the internal pressure in the piston unit. cylinder by the first brake force amplifier 22. The detailed explanations of the advantageous possibilities for increasing the pressure in the piston-cylinder unit and for creating at least one hydraulic braking torque with the aid of the first brake force amplifier 22 , will be detailed below. The increase of the internal pressure of the piston-cylinder unit with the aid of the first brake force amplifier 22 is realized in a relatively simple manner. In particular, such an increase is generally faster to perform than the establishment of a hydraulic braking torque of a wheel brake cylinder by the operation of at least one pump of a hydraulic brake circuit. The first brake force amplifier, for example, comprises a motor 24 which displaces an assistance piston 26I independently of the input piston 16. The assistance piston 26 touches, for example, the side of the reaction disc 18 turned towards the In particular, the inlet piston 16 at least partially passes through the cavity of the assist piston 26.

The force-transmitting contact between the first force amplifier 22 and the output piston 12 does not necessarily pass through the assist piston 26 and / or the reaction disk 18. The above-described equipment of the control system brakes with a reaction disc 18 and the assist piston 26, should be taken only as an example. In addition, the braking system is not limited to some embodiment of the components 12, 16 and / or 26. The usable shapes of the components 12, 16 and 26 are thus virtually any. The first brake force amplifier 22 is an electromechanical brake force amplifier and / or a brake force hydraulic amplifier. In particular, the first brake force amplifier is an adjustable / continuously controlled brake force amplifier. But the first brake force amplifier 22 is not limited to a certain type of brake force amplifier. Preferably, the first brake force amplifier 22 is controlled by taking into account a determined quantity relative to the control of the brake actuating element 10 exerted by the driver such as, for example, the transmission of a brake. brake force and / or brake stroke seized. By way of example, for controlling the first brake force amplifier 22, the signal supplied by a force sensor 28 for the brake force Fb exerted by the driver on the brake actuating element 10 is used. variant or additionally, the control of the first brake force amplifier is also taking into account the difference in stroke according to which the input piston 16 is in relation with the assistance piston 26. Such a differential race is determined by means of a stroke sensor 30. The stroke sensor 30 is for example a magnetic sensor, in particular a Hall effect sensor. But for the sensors 28, 30, there is a large number of other types of sensors. Likewise, the braking system described is not limited to an embodiment with sensors 28 and 30. As an option, the brake system is equipped with a second brake force amplifier 32. However, it is not possible to equip the brake system. brake system with the second brake force amplifier 32, in particular insofar as the spring device 20 has a force / stroke spring characteristic corresponding to a preferred characteristic (according to the standards) of the actuating element 10. In this case, it is not necessary to use a second brake force amplifier to improve the perception (feel) of actuation / perception of brake (pedal feel) for the driver. The second brake force amplifier 32 is an electromechanical brake force amplifier and / or a hydraulic brake force amplifier. The second brake force amplifier 32 may also be an adjustable / continuously controlled brake force amplifier. The second brake force amplifier 32 comprises a motor 34 connected to the input rod 16 (pusher) by a force transmission element / coupling element 36. For the two brake force amplifiers 22 and 32, can use models with identical basic structure. This reduces the cost of manufacturing the brake system. The force transmission element 36 may also be designed so that the second brake force amplifier 32 is integrally connected to the input rod (pusher) 16. An important advantage of the brake system equipment with the two brake force amplifiers 22 and 32 result from the use of two substantially identical subsystems and from the multiple use thus ensured of the components according to the operating states of the brake system, that is to say of the vehicle. In particular, the second brake force amplifier 32 gives a very variable impression to the perception of the brake for an actuating stroke different from zero, but lower than a minimum actuating stroke or for a small brake force Fb exerted. by the driver. Advantages

13 particular of the possibility of applying the second brake force amplifier 32, will be detailed later. Advantageously, the brake system comprises at least one electric and / or electromagnetic brake system which exerts a pair of brake-brake installations (non-hydraulic) on at least one wheel. According to a particularly advantageous embodiment, the brake system is a regenerative braking system (dynamic braking system) comprising a generator (not shown). The use of the brake system is however not limited to its cooperation with a generator, as will be described below: FIG. 1A shows the brake system whose brake actuating element 10 is not ordered (Fb = 0); in this case, the brake actuating element 10 and the pistons 12, 16, 26, each occupy its output position. In other words, in such an output state or rest of the brake actuating element 10 and / or pistons 12, 16, 26, it is generally in the rest position. Figure 1B shows a brake system for a slight displacement of the brake actuating element 10 from its output position (Fb 0 0). The brake actuating element 10 is thus displaced from an actuating stroke (x) different from zero (x 0) and smaller than a minimum actuating stroke from its exit position (for x = 0 ). The actuating stroke (x) of the brake actuating element 10 is a displacement stroke of the brake operating element 10 from its rest position for a brake force Fb exerted by the driver. and which is non-zero. In particular, the actuating stroke may mean a pivoting stroke of a lever-shaped component of the brake actuating member 10 about an axis of rotation and / or a translation travel of a component movable in translation of the brake actuating element 10. For an actuating stroke 10 less than the minimum actuating stroke or for a low brake force Fb exerted by the driver, the deformation / compression of the installation of spring 20 by the brake force Fb exerted by the driver prohibits the

14 transmission of the brake force of the driver on the output piston (prohibits this transmission or hinders this transmission). This situation can be realized for example by the spring installation 20 so that the force for deforming / compressing the spring installation 20 for an actuating stroke (x) smaller than the minimum actuating stroke remains lower than the force required to move the inlet piston 16. The minimum actuating stroke can thus be described as an actuating stroke (x) for which the spring device 20 is deformed / compressed sufficiently that the force for the additional deformation / compression in the spring installation 20, which is greater than the friction force opposing the displacement of the inlet piston 16. The advantageous embodiment of the spring installation 20 in the usual brake systems, replaces in general a fixed relation between the actuating stroke of the brake actuating element 10, the hydraulic volume displaced in the piston-cylinder unit and the brake torque hydra resulting from a variable relationship. The replacement of the fixed relation can be considered as the variable relation according to which, because of the advantageous realization of the spring installation, the mechanical connection between the brake actuating element 10 and the piston-cylinder unit will be open. . For this reason, the brake system described here is particularly applicable to energy recovery (dynamic braking). In particular, when the brake actuating element 10 is controlled in an actuating stroke (x) smaller than the minimum actuating stroke, the brake system is particularly suitable for recharging a vehicle battery. As in the usual brake systems, there is generally a fixed connection between the brake actuating element 10 and the piston-cylinder unit which is neutralized, it is possible to use a generator of the brake system to brake the braking system. vehicle without exceeding the braking setpoint desired by the driver. In particular, during the energy recovery, a set value of the overall brake torque to be exerted on the vehicle is determined / set as a function of the control of the brake actuating element 10 by the driver. help of the sensor

Force 28 and / or a brake stroke sensor for determining the actuating stroke (x) or securing it. The generator brake torque exerted by the driver can be adjusted in this case so that the overall brake torque is not exceeded according to the determined / fixed setpoint. Inasmuch as the generator brake torque exerted by the generator is less than the overall brake torque corresponding to the determined / fixed setpoint, the first brake force amplifier 24 establishes a hydraulic brake torque corresponding to the difference the generator brake torque and the overall brake torque as a function of the determined / fixed setpoint. Similarly, insofar as the use of the generator is not desired or possible, for example because the vehicle battery is already fully charged, the first brake force amplifier 24 applies a corresponding hydraulic brake torque. to the set quantity. Under these conditions, the driver does not perceive the activation / neutralization of the generator. In either case, the assist piston 26 will be displaced from an adjustment stroke (y) from its exit position. In addition, the stroke difference (z) between the input piston 16 and the assist piston 26 is different from zero. The second brake force amplifier 32 may also be used during the recovery mode shown in FIG. 1B to improve the feeling or perception of brake actuation / sensation or perception by the driver.

For this, the second brake force amplifier 32 exerts a non-zero restoring force Fr on the brake actuating element 10. The return force Fr thus provided can be established by using the standard reaction of the brake actuating element 10 by actuating the conductor. Thus, the operation of the generator for charging the vehicle battery, will not be perceived by the driver or because of non-compliance with the braking intensity that has been predefined, or because of the different behavior of the actuating element brake 10. The return force Fr supplied by the second brake force amplifier 32 is additively combined with the force of

16 spring exerted by the spring device 20 on the brake actuating element 10, so that even for a relatively reduced force Reduced, provided maximum, this ensures a perception or sensation (perception) of brake or feeling of actuation, advantageous. For the second amplifier of the brake force 32, it is thus possible to use a deformable, economical, and compact module. The brake system can be designed for example to have a separation of the mechanical connection between the brake actuating element 10 and the piston-cylinder unit up to a set value / total brake torque, equal to the maximum the applicable generator torque. In particular, the displacement of the input piston 16 from its output position, can be done only from a minimum brake stroke equal to the total brake torque corresponding to a deceleration of 0.3 g of the vehicle. This can easily be achieved by a suitable design of the spring arrangement 20. Since the second brake force amplifier 32 exists, in addition to its simulator function, during the recovery mode reproduced in FIG. Figure 1B helps, in other modes of recovery, than a brake force amplifier, to increase the internal pressure in the piston-cylinder unit. This situation will be described hereinafter with reference to FIGS. 1C and 1D: FIG. 1C shows the brake system after the displacement of the brake actuating element 10 of at least one minimum actuating stroke. After this movement, the brake system is controlled in direct braking mode in which the spring installation 20 (and to the extent that there is a second brake force amplifier 32), allows a combined movement of the input piston 16 with the brake actuating member 10. The stroke of the rod (not shown) in which the input piston 16 has been driven from its output position with the brake actuating member is preferential, a function of the brake force Fb. In this case, the first brake force amplifier 22 can work in a conventional manner, that is to say provide an assist force for which the differential travel (z) is zero. In other words, the assist force provided by the first brake force amplifier 22 is a function of the brake force of the driver Fb. FIG. 1D shows the brake system for actuating the brake actuating element 10 that predefines a significant deceleration of the vehicle, for example a vehicle setpoint deceleration of at least 0.6 g, in particular at least equal to at 0.8 g. Preferably, for a relatively high setpoint deceleration of the vehicle or for an actuation of the vehicle brake actuating element at least a limit actuating stroke, greater than the minimum actuating stroke, the brake system will be controlled in single brake mode, amplified; in this mode, the second brake force amplifier 32 uses a conventional brake pressure slope. In this case, the second brake force amplifier 32 can exert in an amplified brake mode an additional force Fz that is not turned towards the brake actuating element 10, this force acting on the input piston 16. In particular, the additional force Fz is a function of the brake force Fb exerted by the driver, so that the stroke of the piston of the input piston is a function of the brake force Fb exerted by the driver. Correspondingly, the assist force provided by the first brake force amplifier 22 (unsharpened) is also the driver brake force Fb corresponding to this function, so that the differential travel (z) remains equal to zero. . The process steps described in the above paragraphs are achievable by the brake system equipped with a controller that applies control signals to exert one of the current operating modes as a function of the force for the first amplifier. brake force 22 (and optionally also the second brake force amplifier 32). As the realization of such a control device is obvious if we refer to the description of the different modes of operation, this description will not be detailed here.

Figures 2A-2D show schematic views of a second embodiment of the brake system in different modes of operation. The brake system reproduces schematically in part in Figures 2A-2D comprises the components 10, 12, 16-26 and 30-34 already described and which will not be redescribed. To determine the magnitude of the actuating stroke (x) of the brake actuating element 10, the brake system comprises a brake stroke sensor 40 which is for example a magnetic sensor, in particular a Hall effect sensor. . The system described below is however not limited to equipment with such a brake stroke sensor 40. The brake system has no integral coupling between the second brake force amplifier 32 and the input piston. 16. Instead, the second brake force amplifier 32 is connected by a connecting member 42 to the input piston 16 and / or the brake actuating member 10 to have a lockable idle stroke. . The element 42 comprises a first coupling element 44 and a second coupling element 46. When the first coupling element 44 is activated, the input rod 16 is integrally coupled to the second brake force amplifier 32; that is, there is an integral connection between the second brake force amplifier 32 and the input rod 16. The second coupling element 46 connects the second brake force amplifier 32 integrally with the brake element. actuation of the brake 10, that is to say with a component adjustable in translation, connected to the brake actuating element 10. The cooperation between the two brake force amplifying elements 22 and 32 can thus be order. The two coupling elements 44 and 46 may for example be two electrically commutated clutches. Figure 2A shows the brake system when the brake operating element 10 is not controlled (Fb = 0). In other words, in such an output position, the brake actuating element 10 and the pistons 12, 16, 26 maintain their rest position. The

19 brake stroke (x), the differential stroke (z) and the stroke (y) of the piston of assistance piston 26, are zero. FIG. 2B shows the brake system when the brake actuating element 10 is displaced by the brake force Fb exerted by the driver, of an actuating stroke (x) different from zero, but lower than the race minimum actuation. In this mode of operation, the brake stroke (x) will be detected by the brake stroke sensor 40 and it will be used to set a reference quantity relating to the total brake torque to be exerted on the vehicle.

Then, as already described above, with the aid of the first brake force amplifier 22, it is possible to exert a hydraulic brake torque corresponding to the difference between the total brake torque according to the set reference quantity and the torque of the brake. generator brake currently exercised by a generator. Thus, even in this embodiment of the brake system, it is possible to recharge the battery of the vehicle while respecting the braking intensity predefined by the driver, that is to say by executing it according to the fixed reference quantity. To improve the perception of the actuation / perception of the brake (also called pedal sensation) of the brake actuating element 10, it is possible to use the second brake force amplifier 32. Firstly, the first coupling element 44 of the connecting element 42, can be activated, the second coupling element 46 not being activated so as to have an integral coupling between the input rod 16 and the second brake force amplifier 32, but not of integral connection between the second brake force amplifier 32 and the brake actuating element 10. In case, at the spring installation 20 and the second brake force amplifier 32, prohibit the transmission of the brake force Fb exerted by the driver, on the output piston by closing the first coupling element 44 during the actuation of the brake actuating element 10 of a non-zero actuating stroke, but less than the stroke of actio minimal, the input piston 16 can be maintained in its output position. At the same time, at least with the aid of the deformation of the spring device 20, a reaction effect is generated for the driver in response to the actuation of the brake actuating element 10. appropriate embodiment of the spring installation 20 and / or by exerting a restoring force on the brake actuating element 10, with the second brake force amplifier 32, the reaction effect is adapted according to a characteristic of preferred actuation (according to the standard) of the brake actuating element 10. FIG. 2C shows the brake system after the displacement of the brake actuating element 10 of the actuating stroke which corresponds to at least the minimum actuating stroke corresponding for example to a setpoint deceleration of the vehicle equal to 0.3 g. Preferably, this controlled direct braking mode will have begun if the minimum actuating stroke is exceeded by the activation of the second coupling element 46 in addition to the first coupling element 44. two coupling elements 44, 46, an integral connection connects the inlet piston 16 and the brake actuating element 10. Thus, after activation of the two coupling elements 44, 46, the inlet piston 16 and the the brake actuating element 10 and thus also the output piston 12 connected to the brake actuating element 10 will be movable in common. This produces direct braking by the driver after activation of the two coupling elements 44, 46. The second brake force amplifier 32 may have, due to the reduced requirements of the force to be transmitted, a moment of inertia so low. that the second brake force amplifier 32, follows the brake actuating element 10 and the stroke of the inlet piston 16. In this direct braking mode, the first brake force amplifier 22 preferably operates in a controlled manner. traditional so that the assistance force provided by the first brake force amplifier 22 is a function of the brake force Fb exerted by the driver. In other words, the first brake force amplifier 22 regulates the differential travel (z) to a zero value. At the same time, the driver's brake stroke is adjustable to match the conventional brake stroke characteristic for the driver.

FIG. 2D shows the brake system for an actuating stroke (x) which corresponds at least to the limit actuating stroke for predefining a relatively high setpoint deceleration for the vehicle. This corresponds for example to a deceleration (braking) of the vehicle of at least 0.6 g and in particular a reference deceleration of at least 0.8 g, given by the driver. In this case, the brake system switches to the amplified direct braking mode in which the two coupling elements 44, 46 are deactivated and the two brake force amplifiers 22, 32 are controlled to operate in a conventional manner. The first brake force amplifier 22 is thus preferably controlled so that the differential travel (z) is equal to zero. Advantageously, the second brake force amplifier 32 is controlled in the amplified direct braking mode so that the brake stroke (x) corresponds to the conventional brake travel characteristic for the driver. In other words, the second brake force amplifier 32 assists the function of the first brake force amplifier to achieve a particularly important setpoint deceleration. The embodiments described above have the advantage of using the second brake force amplifier 32 as a pedal simulator for recovery up to maximum recovery deceleration. In addition, the two brake force amplifiers 22, 32 are used additionally to generate a high hydraulic brake torque acting on at least one wheel.

This allows in particular to use a second brake power amplifier 32 small and economical. Depending on the state of operation of the brake system, the two brake force amplifiers 22, 32 controlled independently of one another can also be controlled in opposition. The brake system with its two brake force amplifiers 22, 32 thus offers a high dynamic. Another advantage of these embodiments, compared to a conventional braking system equipped with a single brake force amplifier, is the high residual functionality available in the event of failure of one of the two.

22 brake amplifiers 22, 32. At the same time, all the embodiments described above, allow a direct mechano-hydraulic action of the brake actuating element 10 on the wheel brake cylinders in case failure of one of the two brake force amplifiers 22, 32, for example because of the interruption of the power supply. Figure 3 shows a flow chart showing an embodiment of the method of managing a vehicle brake system. The method is applied by a braking system equipped with a brake actuating element, an input piston which, when controlling the brake actuating element in at least one actuating stroke predefined minimum, will be moved so that the brake force exerted by the driver, is transmitted by the brake actuating element and the displacement of the inlet piston on an output piston to thereby increase the internal pressure of the unit piston-cylinder brake system; the system also includes a spring arrangement which will be deformed to prohibit transmission of the brake force exerted by the driver on the output piston when the brake actuating member is controlled by a non-zero actuating stroke but less than the minimum actuation stroke. The brake system according to the invention comprises a first brake force amplifier and at least one electrical and / or magnetic brake installation, such as, for example, a generator and / or a parking brake.

According to the method step S1, when controlling the brake actuating element according to an actuating stroke different from zero and lower than the minimum actuating stroke, this actuation will be detected. The actuation of the brake actuating element is detected for example by means of a force sensor and / or a stroke sensor. Then, a set amount is set concerning the total brake torque to be exerted on the vehicle taking into account the control of the brake actuating element. In the following process step S2, at least one electrical and / or magnetic brake installation is controlled in a mode in which the brake torque of the electric brake system

23 and / or magnetic, is less than or equal to the total brake torque corresponding to the set target quantity, acting on at least one wheel of the vehicle. Preferably, the generator is controlled as an electric and / or magnetic brake installation to exert a generator brake torque which represents at least a portion of the brake torque of the brake system exerted on at least one wheel of the vehicle . The method described here can thus be used advantageously, in particular to recharge a vehicle battery.

In the process step S3 performed before, simultaneously with or after the method step S2, the first brake force amplifier taking into account the difference between the total brake torque corresponding to the set reference quantity and the brake torque. provided by the electrical and / or magnetic brake system is controlled so that the output piston is moved by the first brake force amplifier and the pressure in the piston-cylinder unit is adjusted again. This has the advantages already described above. For example, in the case of decreasing generator brake torque, the (inner) pressure in the piston-cylinder unit can be increased in the process step S3. The total brake torque exerted on the vehicle, thus, even after the battery is fully recharged or after a braking of the vehicle, can be maintained by a speed lower than the minimum speed of actuation of the generator, according to a value predefined by the driver. Thus, in the event of a reduction in the brake demand requested by the driver and / or an increase in the brake torque of the generator, the internal pressure will be reduced in step S3 to respect the total brake torque. The new adjustment of the internal pressure thus means the adaptation to the brake demand setpoint of the currently applied generator brake torque or the corresponding brake torque of the electric and / or magnetic brake system. Optionally, if the actuation of the brake operating element is detected for an actuating stroke different from zero and smaller than the minimum actuating stroke, the

24 second brake force amplifier can exert on the brake actuating element, a reaction force. Upon detection of the actuation of the brake actuating element at least a predetermined limit actuation stroke greater than the minimum actuation stroke, the second brake force amplifier may be used to exert on the input piston, an additional force directed towards the output piston. A particularly advantageous function of the second brake force amplifier is particularly ensured if the detection of the actuation of the brake actuating element of an actuating stroke different from zero and lower than the actuating stroke minimum, the input piston is coupled to the second brake force amplifier. In addition, in case of detection of the control of the brake actuating element in a minimum actuating stroke, the brake actuating element will be further coupled to the second brake force amplifier. Thus, the driver can brake directly by acting on the piston-cylinder unit. It is also advantageous for the detection of the actuation of the brake actuating element of at least one predefined limit actuation stroke, the inlet piston and the brake actuating element 10, will be decoupled from the second brake force amplifier. The energy applied to deform / compress the brake system, is thus used in a direct braking operation, strong, to establish a high internal pressure in the piston-cylinder unit.

The process steps described above may also be performed by the brake system controller described above, so that a more detailed description of the controller in this context is unnecessary. 30 s NOMENCLATURE

10 brake actuating element 12 output piston 14 direction of movement 16 input piston 18 reaction disk 20 spring 22 first brake force amplifier 24 motor 26 assist piston 28 force sensor 30 stroke sensor 32 second brake force amplifier 15 34 motor 36 force transmission element 40 brake stroke sensor 42 connecting element 44 first coupling element 20 46 second coupling element

Claims (1)

CLAIMS1 »A vehicle brake system comprising: - a brake operating element (10), - an input piston (16) which, when controlling the brake operating element (10), is displaced at least a predetermined minimum actuating stroke from its output position; - an output piston (12) to which the brake force (Fb) exerted by the driver on the actuating element of the actuator is transmitted; brake (10) by the displacement of the inlet piston (16), so as to place the output piston (12) to increase the pressure in a piston-cylinder unit of the brake system, and - a first force amplifier of brake (22) characterized by a spring arrangement (20) by which the input piston (16) is mounted on the brake actuating member (10) so that actuating the brake actuating element (10) with an actuating stroke (x) different from zero and lower at a minimum actuating stroke, the spring device (20) is deformed so as to prohibit the transmission of the brake force (Fb) exerted by the driver, the displaced brake actuating member (10) the actuating stroke (x) on the output piston (12); when actuating the brake actuating element (10) with an actuating stroke (x) different from zero and smaller than the minimum actuating stroke, the output piston (12) is displaced by the first brake force amplifier (22) to thereby increase the pressure in the piston-cylinder unit. Brake system according to claim 1, characterized in that for the control of the brake actuating element (10) an actuating stroke (x) different from zero and lower than the actuating stroke minimum, the spring installation (20) is compressed so that the input piston (16) remains in its output position. Brake system according to claim 1 or 2, characterized in that the spring arrangement (20) has a force-stroke spring constant which corresponds to the constant force-stroke of the brake pedal. 4 »Brake system according to claim 1, characterized in that the brake system comprises at least one electrical and / or magnetic brake installation and a control device, and the control device is designed to detect the control of the brake system. brake actuating element (10) with an actuating stroke (x) different from zero and smaller than the minimum actuating stroke; - for setting a set amount relating to the overall brake torque to be exerted on the vehicle taking into account the control of the brake actuating element (10), - for controlling at least one electrical and / or magnetic brake installation in a mode in which the brake torque of the electric brake system and / or magnetic is less than or equal to the total brake torque, corresponding to the fixed target quantity, exerted on at least one wheel of the vehicle, and - to control the first brake force amplifier (22) in taking into account the difference between the total brake torque corresponding to the set reference quantity and the brake torque of the electric and / or magnetic brake system so that the output piston (12) is displaced by the first amplifier of brake force (22) and adjusts the pressure in the piston-cylinder unit again. Braking system according to claim 4, characterized in that at least one electrical and / or magnetic brake system comprises a generator exerting a generator brake torque at least for a portion of the brake torque of the brake system. The braking system as claimed in claim 1, characterized in that it comprises a second brake force amplifier (32) by which, at least during the actuation of the brake force brake actuating element (10) of an actuating stroke (x) different from zero and smaller than the minimum actuating stroke; - a restoring force (Fr) is exerted on the actuating element brake (10), and / or - at least for an actuation of the brake actuating element (10) of at least one predetermined limit actuating stroke, greater than the minimum actuating stroke, a complementary force (Fz) directed towards the output piston (1 2) is exerted on the inlet piston (16). 7 »Brake system according to claim 6, characterized in that the second brake force amplifier (32) is connected to the input piston (16) by a force transmission element (36). Brake system according to claim 6, characterized in that the second brake force amplifier (32) is connected to the input piston (16) and to the brake actuating element (10) by an element link (42) for a lockable idle stroke. 9 »Brake system according to claim 7, characterized in that the connecting element (42) comprises a first coupling element (44) coupling the second brake force amplifier (32) to the input rod (16). ) and a second coupling element (46) coupling the second brake force amplifier (32) to the brake actuating element (10). Brake system according to claim 9, characterized in that in the control device, for a control of the brake operating element (10) an actuating stroke (x) different from zero. and less than the minimum actuation stroke, the first coupling element (44) is controlled in an active mode and the second coupling element (46) is switched to inactive mode, and - for a control of the element of brake actuation (10) of a minimum actuating stroke, the first coupling element (44) and the second coupling element (46) are switched in the active mode, and - for a control of the element at least one of the predetermined limit actuation stroke, the first coupling element (44) and the second coupling element (46) are switched to inactive mode. 11 »A method of managing a vehicle brake system comprising - a brake actuating member (10), an input piston (16) which for actuating the brake actuating member (10) is displaced by at least one predetermined minimum actuation stroke from its output position so that a brake force (Fb) exerted by the driver on the brake actuating member (10) is transmitted to an output piston (12) by the input piston (16), moved to move the output piston and thereby increase the pressure in a piston-cylinder unit of the brake system, - a spring arrangement (20) which, upon actuation of the brake actuating member (10) with an actuating stroke (x) different from zero and smaller than the minimum actuating stroke, is deformed to prohibit the transmission of the brake force (Fb) exerted by the driver by the brake operating element (10) d placed the actuating stroke (x) on the output piston (12), - a first brake force amplifier (22), and - at least one electrical and / or magnetic brake system, characterized by the steps following steps: 30 - detecting from the control of the brake actuating element (10) the actuating stroke (x) different from zero and lower than the minimum actuating stroke and setting a torque setpoint the total brake force to be exerted on the vehicle by taking account of the control of the brake actuating element (10), - controlling at least one electrical and / or magnetic brake installation in a mode in which the brake torque of the installation of electric and / or magnetic brakes is less than or equal to the total brake torque corresponding to the fixed set value exerted on at least one wheel of the vehicle, and - controlling the first brake force amplifier (22) in taking comp the difference between the total brake torque corresponding to the set target quantity and the brake torque of the electric and / or magnetic brake system for moving the output piston (12) by the first force amplifier; brake (22) and adjust the pressure in the piston-cylinder unit again. 12 »The method of claim 11, characterized in that the generator is controlled as at least one electrical and / or magnetic brake system, so as to exert the brake torque of the generator as at least a portion of the brake torque of the installation of brakes on at least one wheel of the vehicle. 13 »Method according to claim 11 or 12, characterized in that during the control of the brake actuating element (10) following the actuating stroke (x) different from zero and lower than the actuating stroke minimum, the second brake force amplifier (32) exerts a restoring force (Fr) on the brake operating element (10) and / or when controlling the brake operating element (10). ) of at least one predefined limit actuation stroke greater than the minimum actuation stroke, an additional force (Fz) directed to the output piston (12) is exerted by the second brake force amplifier (32) on the inlet piston (16). The method according to claim 13, characterized in that for controlling the actuation of the brake actuating element (10) with an actuating stroke (x) different from zero and less than minimum actuating stroke, the input piston (16) is coupled to the second brake force amplifier (32) and - for controlling the brake actuating element (10) of a stroke of minimum actuation, the brake actuating element (10) is further coupled to the second brake force amplifier (32). 15 »Method according to claim 13 or 14, characterized in that during the actuation of the brake actuating element (10) at least of the predetermined limit actuation stroke, the inlet piston (16 ) and the brake actuating element (10) are decoupled from the second brake force amplifier (32). 25